This is an early prototype of the game Prey by 3D Realms, from November of 1995.
You can either pass a map name as the argument when launching it, i.e. 'prey demo4', or once launched via 'prey', press TAB to open the console and then type 'load demo4'.
You'll also notice several demos are available (DMO files) which can be played by using the 'play <demoname>' command.
You can use W to change the display mode - it defaults to wireframe mode. L will enable auto-leveling. X will strafe left and C will strafe right. A and Z will go up or down. And as mentioned, TAB will open the console.
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